Portable electronic devices including wearable devices such as earphones, headsets, and hearing aids are recently increasingly miniaturized, and power sources are increasingly implemented as secondary batteries. When a power source is a secondary battery, it is conceivable that a method of battery charge includes inserting a connector of a charging cable into a portable electronic device; however, the operation of inserting a connector of a charging cable is cumbersome. If the structure of the connector is made easily insertable, this makes waterproofing difficult. In this regard, battery charge utilizing non-contact power transmission eliminates the cumbersome operation of inserting a connector to the portable electronic device and makes it easy to achieve a waterproof structure. Patent Document 1 discloses an example of applying a non-contact power transmission technique to a hearing aid. In this hearing aid, at least a portion of a power receiving module (such as a power receiving coil) is disposed along a surface shape of any one or more of an outer wall member of a hearing aid body, an outer wall member of an ear mold, and an outer wall member of a coupling portion.